This invention relates in general to vehicle axle assemblies and in particular to an improved structure for a banjo-type axle housing.
Axle assemblies are well known structures which are in common use in most vehicles. Such axle assemblies include a number of components which are adapted to transmit rotational power from an engine of the vehicle to the wheels thereof. Typically, an axle assembly includes a differential which is rotatably supported within a non-rotating carrier. The differential is connected between an input drive shaft extending from the vehicle engine and a pair of output axle shafts extending to the vehicle wheels. The axle shafts are contained in respective non-rotating tubes which are secured to the carrier. Thus, rotation of the differential by the drive shaft causes corresponding rotation of the axle shafts. The carrier and the tubes form a housing for these drive train components of the axle assembly, inasmuch as the differential and the axle shafts are supported for rotation therein.
Axle housings are generally classified into two basic types. The first axle housing type is a unitized carrier construction, commonly referred to as a Salisbury or Spicer type axle assembly. In this structure, the carrier (which houses the rotatable differential) is directly connected to the two tubes (which house the rotatable axle shafts). An opening is provided at the rear of the carrier to permit assembly of the differential therein. This opening is closed by a cover during use.
The second axle housing type is a separable carrier construction. In this structure, the axle tubes are connected together by a central member which is formed separate and apart from the carrier. This central member is generally hollow and cylindrical in shape, having a large generally circular opening formed therethrough. During assembly, the differential is first assembled within the carrier, then the carrier is secured to the central member. The overall shape of this type of axle housing (i.e., the generally round shape of the central member and the elongated tubes extending therefrom) generally resembles the shape of a banjo musical instrument. Hence, this type of axle housing is commonly referred to as a banjo-type axle housing. Banjo-type axle housings are advantageous because the carrier and differential can be removed from the axle assembly for service without disturbing the other components thereof.
One known structure for a banjo-type axle housing is formed by splitting one end of each of two tubes, spreading the two split ends apart, and securing the spread ends together to form a hollow cylindrical central member. The central member includes rearwardly and forwardly facing openings. A rear mounting plate and cover are secured over the rearwardly facing opening and a forward mounting plate is secured over the forwardly facing opening. The forward mounting plate includes a generally oval shaped opening which receives a differential and carrier assembly. Typically, a pair of baffle plates are secured within the axle housing central member to cover the interior ends of the axle tubes. The baffle plates have apertures formed therethrough through which the axle shafts extend. The baffle plates function to prevent the splashing of differential lubricant out of the central member into the axle tubes.
The above-described banjo-type axle housing has been in common use for years. However, it has been found that under typical vertical loading conditions, the axle housing develops tensile stresses within the curved portions of the spread apart tube ends which form the central member. These tensile stresses can cause the central member of the axle housing to fracture at or near the curved portions. Thus, it would be desirable to provide an improved structure for a banjo-type axle structure which is resistant to these tensile stresses and, therefore, has a longer useful life. Also, it would be desirable to provide an improved structure for a banjo-type axle housing which is simple and inexpensive in construction.